More than a dozen sailors on board an Indian Navy submarine are feared dead after it caught fire, exploding and partially sinking at a naval dockyard in Mumbai. India’s defense minister A. K. Antony confirmed that navy personnel had died in the explosion.

Earlier reports stated that at least 18 people were believed to
be on board when the submarine caught fire.

It's said to be the worst accident for the navy's submarine fleet
since India’s 1971 war with Pakistan. The explosion sent a huge
fireball into the air and had nearby sailors jumping into the sea
in panic.
"There was an explosion immediately after midnight in the forward
side of the submarine, where missiles and torpedoes are kept to
be used whenever necessary," a naval source told Reuters.
"Now the submarine is tilted on the front side and all hatches
are closed. They are trying to open those now."

Divers were desperately trying to pry open the hatches of the
vessel.

Defense Minister A.K. Antony gave no other details but said he
felt sad about the loss of lives. “It’s a loss to all of us.
It’s a tragedy,” Antony told reporters before leaving for
Mumbai to monitor the situation.

The blast happened on the INS Sindhurakshak around midnight and
was shortly followed by a massive fire. Many of the sailors on
board the submarine reportedly managed to jump off to safety, but
more than a dozen are feared trapped inside the hull. The vessel
partially submerged after the fire. Several people have
reportedly been rushed to hospital following the incident.

Fire brigades were battling the blaze for almost three hours to
prevent the fire spreading to other vessels docked nearby. The
INS Sindhuratna, which was docked close to the Sindhurakshak, was
pulled away to safety.

Although it's believed that the explosion onboard the Indian
submarine was likely an accident, an investigation was launched
to establish the exact cause, the navy said.

The number of crew in the boat when fully operational is 110. One
or two men are usually on duty on top of the submarine, according
to the source. They either jumped into the water or were thrown
off by the force of the explosion.

There was no immediate comment on the status of the sunken
submarine’s torpedoes and other weapons.

"Lot of things are in very close proximity, there is fuel,
there is hydrogen, there is oxygen, there are weapons with high
explosives on board," retired Indian navy chief Arun Prakashs
said. "So a slightest mistake or slightest accident can
trigger off a huge accident.”

The Sindhurakshak is a 16-year-old Russian-made submarine which
recently underwent an overhaul and upgrade. The Indian Navy spent
some $80 million on the upgrade and expected the vessel to be
operational for at least another 10 years.

The submarine was involved in a previous incident in February
2010, when an explosion in the submarine’s battery compartment
started a fire aboard, killing one sailor and injuring two
others.

A source told India Today that this week’s explosion was likely
caused by a leak of hydrogen gas during battery recharging – the
same reported cause of the 2010 incident. The damage the
submarine sustained three years ago prompted a 2 1/2 year refit
in Russia.

India's fleet of 14 submarines is said to be in urgent need of
modernization, hampered by delays in prompt government decisions
as it confronts corruption allegations.